Process for producing porous materials

ABSTRACT

The present invention relates to a process for preparing a porous material, at least providing a mixture (I) comprising a composition (A) comprising components suitable to form an organic gel and a solvent (B), reacting the components in the composition (A) in the presence of the solvent (B) to form a gel, and drying of the gel obtained in step b), wherein the composition (A) comprises a catalyst system (CS) comprising a catalyst component (C1) selected from the group consisting of alkali metal and earth alkali metal, ammonium, ionic liquid salts of a saturated or unsaturated monocarboxylic acid and a carboxylic acid as catalyst component (C2). The invention further relates to the porous materials which can be obtained in this way and the use of the porous materials as thermal insulation material and in vacuum insulation panels, in particular in interior or exterior thermal insulation systems as well as in water tank or ice maker insulation systems.

The present invention relates to a process for preparing a porousmaterial, at least providing a mixture (I) comprising a composition (A)comprising components suitable to form an organic gel and a solvent (B),reacting the components in the composition (A) in the presence of thesolvent (B) to form a gel, and drying of the gel obtained in step b),wherein the composition (A) comprises a catalyst system (CS) comprisinga catalyst component (C1) selected from the group consisting of alkalimetal and earth alkali metal, ammonium, ionic liquid salts of asaturated or unsaturated monocarboxylic acid and a carboxylic acid ascatalyst component (C2). The invention further relates to the porousmaterials which can be obtained in this way and the use of the porousmaterials as thermal insulation material and in vacuum insulationpanels, in particular in interior or exterior thermal insulation systemsas well as in water tank or ice maker insulation systems.

Porous materials, for example polymer foams, having pores in the sizerange of a few microns or significantly below and a high porosity of atleast 70% are particularly good thermal insulators on the basis oftheoretical considerations.

Such porous materials having a small average pore diameter can be, forexample, in the form of organic aerogels or xerogels which are producedwith a sol-gel process and subsequent drying.

In the sol-gel process, a sol based on a reactive organic gel precursoris first produced and the sol is then gelled by means of a crosslinkingreaction to form a gel. To obtain a porous material, for example anaerogel, from the gel, the liquid has to be removed. This step willhereinafter be referred to as drying in the interests of simplicity.

WO 95/02009 discloses isocyanate-based xerogels which are particularlysuitable for applications in the field of vacuum insulation. Thepublication also discloses a sol-gel-based process for producing thexerogels, in which known, inter alia aromatic, polyisocyanates and anunreactive solvent are used. As further compounds having active hydrogenatoms, use is made of aliphatic or aromatic polyamines or polyols. Theexamples disclosed in the publication comprise ones in which apolyisocyanate is reacted with diaminodiethyltoluene. The xerogelsdisclosed generally have average pore sizes in the region of 50 μm. Inone example, mention is made of an average pore diameter of 10 μm.

WO 2008/138978 discloses xerogels which comprise from 30 to 90% byweight of at least one polyfunctional isocyanate and from 10 to 70% byweight of at least one polyfunctional aromatic amine and have a volumeaverage pore diameter of not more than 5 microns.

WO 2011/069959, WO 2012/000917 and WO 2012/059388 describe porousmaterials based on polyfunctional isocyanates and polyfunctionalaromatic amines, where the amine component comprises polyfunctionalsubstituted aromatic amines. The porous materials described are producedby reacting isocyanates with the desired amount of amine in a solventwhich is inert toward the isocyanates. The use of catalysts is knownfrom WO 2012/000917 and WO 2012/059388.

However, the materials properties, in particular the mechanicalstability and/or the compressive strength and also the thermalconductivity, of the known porous materials based on polyurea are notsatisfactory for all applications. In particular, the thermalconductivities in the ventilated state are not sufficiently low. In thecase of open-cell materials, the ventilated state is the state underambient pressure of air, whereas in the case of partially or completelyclosed-cell materials such as rigid polyurethane foams this state isreached only after aging, after the cell gas has gradually beencompletely replaced.

A particular problem associated with the formulations based onisocyanates and amines which are known from the prior art are mixingdefects. Mixing defects occur as a result of the high reaction ratebetween isocyanates and amino groups, since the gelling reaction hasalready proceeded a long way before complete mixing. Mixing defects leadto porous materials having heterogeneous and unsatisfactory materialsproperties.

In particular for applications in the building sector, a high mechanicalstability is necessary.

It was therefore an object of the invention to avoid the abovementioneddisadvantages. In particular, a porous material which does not have theabovementioned disadvantages, or has them to a reduced extent, should beprovided. The porous materials should have a low thermal conductivity inthe ventilated state, i.e. at atmospheric pressure. Furthermore, theporous material should at the same time have a high porosity, a lowdensity and a sufficiently high mechanical stability.

According to the present invention, this object is solved by a processfor preparing a porous material, at least comprising the steps of:

-   -   a) providing a mixture (I) comprising        -   (i) a composition (A) comprising components suitable to form            an organic gel and        -   (ii) a solvent (B),    -   b) reacting the components in the composition (A) in the        presence of the solvent (B) to form a gel, and    -   c) drying of the gel obtained in step b),    -   wherein the composition (A) comprises a catalyst system (CS)        comprising        -   a catalyst component (C1) selected from the group consisting            of alkali metal and earth alkali metal, ammonium, ionic            liquid salts of a saturated or unsaturated monocarboxylic            acid and        -   a carboxylic acid as catalyst component (C2).

The porous materials of the present invention are preferably aerogels orxerogels.

Preferred embodiments may be found in the claims and the description.Combinations of preferred embodiments do not go outside the scope of thepresent invention. Preferred embodiments of the components used aredescribed below.

According to the present invention, in the process for preparing aporous material a mixture (I) comprising a composition (A) comprisingcomponents suitable to form an organic gel and a solvent (B) is providedin step a). Composition (A) comprises a catalyst system (CS) comprisinga catalyst component (C1) selected from the group consisting of alkalimetal and earth alkali metal, ammonium, ionic liquid salts of asaturated or unsaturated monocarboxylic acid and a carboxylic acid ascatalyst component (C2).

According to step b) the components in composition (A) are reacted inthe presence of the solvent (B) to form a gel. The gel is then driedaccording to step c) of the process of the present invention.

The process as disclosed above results in porous materials with improvedproperties, in particular improved compressive strength and low thermalconductivity.

Composition (A) comprises a catalyst system (CS) which is also denotedas component (a0) in the following. The catalyst system (CS) comprisescatalyst components (C1) and (C2). The catalyst component (C1) isselected from the group consisting of alkali metal and earth alkalimetal, ammonium, ionic liquid salts of a saturated or unsaturatedmonocarboxylic acid. In principle, any alkali metal or earth alkalimetal salt of a saturated or unsaturated monocarboxylic acid or ammoniumor ionic liquid salt can be used in the context of the presentinvention. It is also possible to use mixtures of two or more alkalimetal or earth alkali metal salts of a saturated or unsaturatedmonocarboxylic acid in the context of the present invention.

Preferably, catalyst component (C1) is selected from the groupconsisting of alkali metal and earth alkali metal, ammonium, ionicliquid salts of a saturated or unsaturated monocarboxylic acid with 2 to8 carbon atoms, more preferably, catalyst component (C1) is selectedfrom the group consisting of alkali metal and earth alkali metal,ammonium, ionic liquid salts of a linear saturated or unsaturatedmonocarboxylic acid with 2 to 8 carbon atoms. Particularly preferably,catalyst component (C1) is selected from the group consisting of alkalimetal and earth alkali metal salts of a saturated or unsaturatedmonocarboxylic acid with 2 to 8 carbon atoms, in particular, catalystcomponent (C1) is selected from the group consisting of alkali metal andearth alkali metal salts of a linear saturated or unsaturatedmonocarboxylic acid with 2 to 8 carbon atoms.

It has been found that using an alkali metal or earth alkali metal saltsof saturated or unsaturated monocarboxylic acid with 2 to 8 carbon atomsas a catalyst results in porous materials with improved compressivestrength. In the context of the present invention, alkali metal or earthalkali metal salts of saturated or unsaturated monocarboxylic acids with2 to 6 carbon atoms, in particular linear saturated and unsaturatedmonocarboxylic acids with 2 to 6 carbon atoms are preferably used.Suitable salts are for example sodium salts, potassium salts, or calciumsalts of the respective monocarboxylic acid.

Thus, according to a further embodiment, the present invention isdirected to the process for preparing a porous material as disclosedabove, wherein the catalyst component (C1) is selected from the groupconsisting of alkali metal and earth alkali metal, ammonium, ionicliquid salts of a saturated or unsaturated monocarboxylic acid with 2 to8 carbon atoms.

According to a further embodiment, the present invention is directed tothe process for preparing a porous material as disclosed above, whereinthe catalyst component (C1) is selected from the group consisting ofalkali metal and earth alkali metal salts of a saturated or unsaturatedmonocarboxylic acid with 2 to 8 carbon atoms.

Catalyst system (CS) further comprises a carboxylic acid as catalystcomponent (C2). In principle, any carboxylic acid can be used in thecontext of the present invention. It is also possible to use two or morecarboxylic acids according to the present invention. Preferably,saturated or unsaturated monocarboxylic acids with 2 to 12 carbon atomsare used, for example saturated or unsaturated monocarboxylic acids with2 to 8 carbon atoms, formic acid, acetic acid, propionic acid, sorbicacid, benzoic acid, ethyl hexanoic acid, octanoic acid.

Thus, according to a further embodiment, the present invention isdirected to the process for preparing a porous material as disclosedabove, wherein the catalyst component (C2) is selected from the group ofsaturated or unsaturated monocarboxylic acids with 2 to 12 carbon atoms.

According to a further embodiment, the present invention is directed tothe process for preparing a porous material as disclosed above, whereinthe catalyst component (C1) is selected from the group consisting ofalkali metal and earth alkali metal salts of a saturated or unsaturatedmonocarboxylic acid with 2 to 8 carbon atoms and wherein the catalystcomponent (C2) is selected from the group of saturated or unsaturatedmonocarboxylic acids with 2 to 12 carbon atoms.

Preferably, the catalyst component (C1) is selected from the groupconsisting of alkali metal and earth alkali metal salts of a saturatedor unsaturated monocarboxylic acid with 2 to 8 carbon atoms and whereinthe catalyst component (C2) is selected from the group consisting ofacetic acid and propionic acid.

The amount of catalyst system (CS) used may vary in wide ranges.Suitable amount is for example in the range of from 0.1 to 30% byweight, preferably of from 1 to 20% by weight, more preferred of from 2to 10% by weight, in each case based on the total weight of thecomposition (A).

Thus, according to a further embodiment, the present invention isdirected to the process for preparing a porous material as disclosedabove, wherein the catalyst system (CS) is present in the composition(A) in an amount in the range of from 0.1 to 30% by weight, based on thetotal weight of the composition (A).

According to a further embodiment, the present invention is directed tothe process for preparing a porous material as disclosed above, whereinthe catalyst system (CS) comprises catalyst components (C1) and (C2) ina ratio in the range of from 1:10 to 10:1, preferably in the range offrom 1:5 to 5:1.

The composition (A) may be any composition comprising componentssuitable to form an organic gel. Composition (A) comprises a catalystsystem (CS). Preferably, the composition (A) further comprises at leastone polyfunctional isocyanate as component (a1) and possibly furthercomponents.

According to a further embodiment, the present invention thus isdirected to the process for preparing a porous material as disclosedabove, wherein the composition (A) comprises at least one polyfunctionalisocyanate as component (a1).

Composition (A) may also comprise further components, such as componentswhich react with the polyfunctional isocyanate, one or more catalystsand optionally water. Preferably, the composition (A) comprises at leastone polyfunctional isocyanate as component (a1), and at least onearomatic amine as component (a2), optionally comprises water ascomponent (a3), and optionally comprises at least one catalyst ascomponent (a4).

According to a further embodiment, the present invention therefore isdirected to the process for preparing a porous material as disclosedabove, wherein the composition (A) comprises at least one polyfunctionalisocyanate as component (a1), and at least one aromatic amine ascomponent (a2), optionally comprises water as component (a3), andoptionally comprises at least one further catalyst as component (a4).

The polyfunctional isocyanates (a1) will hereinafter be referred tocollectively as component (a1). Analogously, the aromatic amines (a2)will hereinafter be referred to collectively as component (a2). It willbe obvious to a person skilled in the art that the monomer componentsmentioned are present in reacted form in the porous material.

For the purposes of the present invention, the functionality of acompound is the number of reactive groups per molecule. In the case ofthe monomer component (a1), the functionality is the number ofisocyanate groups per molecule. In the case of the amino groups of themonomer component (a2), the functionality is the number of reactiveamino groups per molecule. A polyfunctional compound has a functionalityof at least 2.

If mixtures of compounds having different functionalities are used ascomponent (a1) or (a2), the functionality of the components is in eachcase given by the number average of the functionality of the individualcompounds. A polyfunctional compound comprises at least two of theabovementioned functional groups per molecule.

For the purposes of the present invention, a xerogel is a porousmaterial which has been produced by a sol-gel process in which theliquid phase has been removed from the gel by drying below the criticaltemperature and below the critical pressure of the liquid phase(“subcritical conditions”). An aerogel is a porous material which hasbeen produced by a sol-gel process in which the liquid phase has beenremoved from the gel under supercritical conditions.

Composition (A) preferably further comprises at least one monool (am).In principle, any monool can be used in the context of the presentinvention. It is also possible according to the present invention thatthe composition (A) comprises two or more monools. The monool can bebranched or linear. Primary, secondary or tertiary alcohols are suitableaccording to the present invention. Preferably, the monool (am) is alinear alcohol, more preferred a linear primary alcohol. The monool canbe an aliphatic monool or an aromatic monool in the context of thepresent invention. Furthermore, the monool can also contain furtherfunctional groups as long as these do not react with the othercomponents under the conditions of the process according to the presentinvention. The monool may for example contain C—C— double bonds or C—Ctriple bonds.

The monool can for example be a halogenated monool, in particular afluorinated monool such as a polyfluorinated monool or a perfluorinatedmonool.

According to a further embodiment, the present invention therefore isdirected to the process for preparing a porous material as disclosedabove, wherein the composition (A) comprises at least one monool (am).

In the context of the present invention, the monool may also be chosenfrom allyl alcohols, alkylphenols, or propargyl alcohol. Furthermore,alkoxylates can be used in the context of the present invention such asfatty alcohol alkoxylates, oxo alcohol alkoxylates, or alkyl phenolalkoxylates.

According to a further preferred embodiment, the monool is selected fromaliphatic or aromatic monools with 1 to 20 carbon atoms. Therefore,according to a further embodiment, the present invention is directed tothe process for preparing a porous material as disclosed above, whereinthe monool is selected from the group consisting of aliphatic monoolswith 1 to 20 carbon atoms and aromatic monools with 1 to 20 carbonatoms.

Suitable primary alcohols are for example linear alcohols such asmethanol, ethanol, propanol, n-butanol, n-pentanol, n-hexanol,n-heptanol, n-octanol, n-nonanol, n-decanol, n-dodecanol,n-tetradecanol, n-hexadecanol, n-octadecanol and n-eicosanol. Suitablebranched primary alcohols are for example isobutanol, isopentanol,isohexanol, isooctanol, isostearyl alcohol and iso-palmityl alcohol,2-ethylhexyl alcohol, 3-n-propyl heptyl alcohol, 2-n-propyl heptylalcohol, and 3-isopropyl heptyl alcohol.

Suitable secondary alcohols are for example isopropanol, sec-butanol,sec-pentanol (pentane-2-ol), pentane-3-ol, cyclopentanol, cyclohexanol,sec-hexanol (hexane-2-ol), hexane-3-ol, secheptanol (heptane-2-ol),heptane-3-ol, sec-decanol and decan-3-ol.

Examples of suitable tertiary alcohols are tert-butanol and tert-amylalcohol.

Generally, the amount of monool present in the composition (A) can varyin wide ranges. Preferably, the monool is present in the composition (A)in an amount of from 0.1 to 30% by weight based on the composition (A),more preferable in an amount of from 0.5 to 25% by weight based on thecomposition (A), in particular in an amount of from 1.0 to 22% by weightbased on the composition (A), for example in an amount of from 1.5 to20% by weight based on the composition (A).

According to a further embodiment, the present invention thus isdirected to the process for preparing a porous material as disclosedabove, wherein the monool is present in the composition (A) in an amountof from 0.1 to 30% by weight based on the composition (A).

Composition (A) comprises components suitable to form an organic gel insuitable amounts. The composition (A) comprises catalyst system (CS) ascomponent (a0). The reaction is for example carried out using from 0.1to 30% by weight of catalyst system (CS) as component (a0), from 25 to94.9% by weight of component (a1), from 0.1 to 30% by weight ofcomponent (a2), from 0 to 15% by weight of water and from 0 to 29.9% byweight of component (a4), in each case based on the total weight of thecomponents (a0) to (a4), where the % by weight of the components (a0) to(a4) add up to 100% by weight.

The reaction is preferably carried out using from 35 to 93.8% by weight,in particular from 40 to 92.6% by weight, of component (a1), from 0.2 to25% by weight, in particular from 0.4 to 23% by weight, of component(a2), from 0.01 to 10 by weight, in particular from 0.1 to 9% by weight,of water and from 0.1 to 30% by weight, in particular from 1 to 28% byweight, of component (a4), in each case based on the total weight of thecomponents (a0) to (a4), where the % by weight of the components (a0) to(a4) add up to 100% by weight.

The reaction is particularly preferably carried out using from 50 to92.5% by weight, in particular from 57 to 91.3% by weight, of component(a1), from 0.5 to 18% by weight, in particular from 0.7 to 16% byweight, of component (a2), from 0.01 to 8% by weight, in particular from0.1 to 6% by weight, of water and from 2 to 24% by weight, in particularfrom 3 to 21% by weight, of component (a4), in each case based on thetotal weight of the components (a0) to (a4), where the % by weight ofthe components (a0) to (a4) add up to 100% by weight.

Within the abovementioned preferred ranges, the resulting gels areparticularly stable and do not shrink or shrink only slightly in thesubsequent drying step.

Component (a1)

In the process of the invention, preferably at least one polyfunctionalisocyanate is reacted as component (a1).

Preferably the amount of component (a1) used is at least 35% by weight,in particular at least 40% by weight, particularly preferably at least45% by weight, especially at least 57% by weight. Preferably the amountof component (a1) used is at most 93.8% by weight, in particular at most92.6% by weight, particularly preferably at most 92.5% by weight,especially at most 91.3% by weight, in each case based on the totalweight of the components (a0) to (a4).

Possible polyfunctional isocyanates are aromatic, aliphatic,cycloaliphatic and/or araliphatic isocyanates. Such polyfunctionalisocyanates are known per se or can be prepared by methods known per se.The polyfunctional isocyanates can also be used, in particular, asmixtures, so that the component (a1) in this case comprises variouspolyfunctional isocyanates. Polyfunctional isocyanates which arepossible as monomer building blocks (a1) have two (hereinafter referredto as diisocyanates) or more than two isocyanate groups per molecule ofthe monomer component.

Particularly suitable polyfunctional isocyanates are diphenylmethane2,2′-, 2,4′- and/or 4,4′-diisocyanate (MDI), naphthylene1,5-diisocyanate (NDI), tolylene 2,4- and/or 2,6-diisocyanate (TDI),3,3′-dimethylbiphenyl diisocyanate, 1,2-diphenylethane diisocyanateand/or p-phenylene diisocyanate (PPDI), trimethylene, tetramethylene,pentamethylene, hexamethylene, heptamethylene and/or octamethylenediisocyanate, 2-methylpentamethylene 1,5-diisocyanate, 2-ethylbutylene1,4-diisocyanate, pentamethylene 1,5-diisocyanate, butylene1,4-diisocyanate,1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (isophoronediisocyanate, IPDI), 1,4- and/or 1,3-bis(isocyanatomethyl)cyclohexane(HXDI), cyclohexane 1,4-diisocyanate, 1-methylcyclohexane 2,4- and/or2,6-diisocyanate and dicyclohexylmethane 4,4′-, 2,4′- and/or2,2′-diisocyanate.

As polyfunctional isocyanates (a1), preference is given to aromaticisocyanates. Particularly preferred polyfunctional isocyanates of thecomponent (a1) are the following embodiments:

-   i) polyfunctional isocyanates based on tolylene diisocyanate (TDI),    in particular 2,4-TDI or 2,6-TDI or mixtures of 2,4- and 2,6-TDI;-   ii) polyfunctional isocyanates based on diphenylmethane diisocyanate    (MDI), in particular 2,2′-MDI or 2,4′-MDI or 4,4′-MDI or oligomeric    MDI, also referred to as polyphenylpolymethylene isocyanate, or    mixtures of two or three of the abovementioned diphenylmethane    diisocyanates or crude MDI which is obtained in the production of    MDI or mixtures of at least one oligomer of MDI and at least one of    the abovementioned low molecular weight MDI derivatives;-   iii) mixtures of at least one aromatic isocyanate according to    embodiment i) and at least one aromatic isocyanate according to    embodiment ii).

Oligomeric diphenylmethane diisocyanate is particularly preferred aspolyfunctional isocyanate.

Oligomeric diphenylmethane diisocyanate (hereinafter referred to asoligomeric MDI) is an oligomeric condensation product or a mixture of aplurality of oligomeric condensation products and thus aderivative/derivatives of diphenylmethane diisocyanate (MDI). Thepolyfunctional isocyanates can preferably also be made up of mixtures ofmonomeric aromatic diisocyanates and oligomeric MDI.

Oligomeric MDI comprises one or more condensation products of MDI whichhave a plurality of rings and a functionality of more than 2, inparticular 3 or 4 or 5. Oligomeric MDI is known and is frequentlyreferred to as polyphenylpolymethylene isocyanate or as polymeric MDI.Oligomeric MDI is usually made up of a mixture of MDI-based isocyanateshaving various functionalities. Oligomeric MDI is usually used inadmixture with monomeric MDI.

The (average) functionality of an isocyanate comprising oligomeric MDIcan vary in the range from about 2.2 to about 5, in particular from 2.4to 3.5, in particular from 2.5 to 3. Such a mixture of MDI-basedpolyfunctional isocyanates having various functionalities is, inparticular, crude MDI which is obtained in the production of MDI.

Polyfunctional isocyanates or mixtures of a plurality of polyfunctionalisocyanates based on MDI are known and are marketed, for example, byBASF Polyurethanes GmbH under the name Lupranat®.

The functionality of the component (a1) is preferably at least two, inparticular at least 2.2 and particularly preferably at least 2.5. Thefunctionality of the component (a1) is preferably from 2.2 to 4 andparticularly preferably from 2.5 to 3.

The content of isocyanate groups in the component (a1) is preferablyfrom 5 to 10 mmol/g, in particular from 6 to 9 mmol/g, particularlypreferably from 7 to 8.5 mmol/g. A person skilled in the art will knowthat the content of isocyanate groups in mmol/g and the equivalentweight in g/equivalent have a reciprocal relationship. The content ofisocyanate groups in mmol/g can be derived from the content in % byweight in accordance with ASTM D-5155-96 A.

In a preferred embodiment, the component (a1) comprises at least onepolyfunctional isocyanate selected from among diphenylmethane4,4′-diisocyanate, diphenylmethane 2,4′-diisocyanate, diphenylmethane2,2′-diisocyanate and oligomeric diphenylmethane diisocyanate. In thispreferred embodiment, the component (a1) particularly preferablycomprises oligomeric diphenylmethane diisocyanate and has afunctionality of at least 2.5.

The viscosity of the component (a1) used can vary within a wide range.The component (a1) preferably has a viscosity of from 100 to 3000 mPa·s,particularly preferably from 200 to 2500 mPa·s.

Component (a2)

Composition (A) can further comprise at least one aromatic amine ascomponent (a2). According to a further embodiment of the presentinvention, at least one aromatic amine is reacted as component (a2). Thearomatic amine is a monofunctional amine or a polyfunctional amine.

According to a further embodiment, the present invention thus isdirected to the process for preparing a porous material as disclosedabove, wherein the at least one aromatic amine is a polyfunctionalaromatic amine.

Suitable monofunctional amines are for example substituted andunsubstituted aminobenzene, preferably substituted aniline derivativeshaving one or two alkyl residues, such as 2,6,-dimethylaniline,2,6-diethylaniline, 2,6-diisopropylaninline, or2-ethyl-6-isopropylaniline.

Preferably, the aromatic amine (a2) is a polyfunctional aromatic amine.According to a further embodiment, the present invention is directed tothe process for preparing a porous material as disclosed above, whereinthe at least one aromatic amine is a polyfunctional aromatic amine.

According to a further embodiment of the present invention, preferablyat least one polyfunctional substituted aromatic amine (a2) having thegeneral formula (I)

where R¹ and R² can be identical or different and are each selectedindependently from among hydrogen and linear or branched alkyl groupshaving from 1 to 6 carbon atoms and all substituents Q¹ to Q⁵ and Q^(1′)to Q^(5′) are identical or different and are each selected independentlyfrom among hydrogen, a primary amino group and a linear or branchedalkyl group having from 1 to 12 carbon atoms, where the alkyl group canbear further functional groups, with the proviso that the compoundhaving the general formula (I) comprises at least two primary aminogroups, where at least one of Q¹, Q³ and Q⁵ is a primary amino group andat least one of Q^(1′), Q^(3′) and Q^(5′) is a primary amino group,is/are reacted as component (a2) in the presence of a solvent (B).

In a preferred embodiment, Q², Q⁴, Q^(2′) and Q^(4′) are selected sothat the compound having the general formula (I) has at least one linearor branched alkyl group, which can bear further functional groups,having from 1 to 12 carbon atoms in the a position relative to at leastone primary amino group bound to the aromatic ring. Component (a2) inthis case comprises polyfunctional aromatic amines (a2-s).

For the purposes of the present invention, polyfunctional amines areamines which have at least two amino groups which are reactive towardisocyanates per molecule. Here, primary and secondary amino groups arereactive toward isocyanates, with the reactivity of primary amino groupsgenerally being significantly higher than that of secondary aminogroups.

The amount of component (a2) used is preferably at least 0.2% by weight,in particular at least 0.4% by weight, particularly preferably at least0.7% by weight, especially at least 1% by weight. The amount ofcomponent (a2) used is preferably at most 25% by weight, in particularat most 23% by weight, particularly preferably at most 18% by weight,especially at most 16% by weight, in each case based on the total weightof the components (a0) to (a4).

According to a further embodiment, the present invention thus isdirected to the process for preparing a porous material as disclosedabove, wherein the at least one aromatic amine (a2) has the generalformula (I)

where R¹ and R² can be identical or different and are each selectedindependently from among hydrogen and linear or branched alkyl groupshaving from 1 to 6 carbon atoms and all substituents Q¹ to Q⁵ and Q^(1′)to Q^(5′) are identical or different and are each selected independentlyfrom among hydrogen, a primary amino group and a linear or branchedalkyl group having from 1 to 12 carbon atoms, where the alkyl group canbear further functional groups, with the proviso that the compoundhaving the general formula (I) comprises at least two primary aminogroups, where at least one of Q¹, Q³ and Q⁵ is a primary amino group andat least one of Q^(1′), Q^(3′) and Q^(5′) is a primary amino group.

According to another further embodiment, the present invention isdirected to the process for preparing a porous material as disclosedabove, wherein composition (A) comprises

-   -   (a0) from 0.1 to 30% by weight of catalyst system (CS),    -   (a1) from 25 to 94.9% by weight of at least one polyfunctional        isocyanate, and    -   (a2) from 0.1 to 30% by weight of at least one polyfunctional        aromatic amine having the general formula I

-   -   -   where R¹ and R² can be identical or different and are each            selected independently from among hydrogen and linear or            branched alkyl groups having from 1 to 6 carbon atoms and            all substituents Q¹ to Q⁵ and Q^(1′) to Q^(5′) are identical            or different and are each selected independently from among            hydrogen, a primary amino group and a linear or branched            alkyl group having from 1 to 12 carbon atoms, where the            alkyl group can bear further functional groups, with the            proviso that the compound having the general formula I            comprises at least two primary amino groups, where at least            one of Q¹, Q³ and Q⁵ is a primary amino group and at least            one of Q^(1′), Q^(3′) and Q^(5′) is a primary amino group,

    -   (a3) from 0 to 15% by weight of water, and

    -   (a4) from 0 to 29.9% by weight of at least one further catalyst,

in each case based on the total weight of the components (a0) to (a4),where the % by weight of the components (a0) to (a4) adds up to 100% byweight and

wherein the sum of the components (a0) and (a4) is in the range of from0.1 to 30% by weight based on the total weight of the components (a0) to(a4).

According to the invention, R¹ and R² in the general formula (I) areidentical or different and are each selected independently from amonghydrogen, a primary amino group and a linear or branched alkyl grouphaving from 1 to 6 carbon atoms. R¹ and R² are preferably selected fromamong hydrogen and methyl. Particular preference is given to R¹═R²═H.

Q², Q⁴, Q^(2′) and Q^(4′) are preferably selected so that thesubstituted aromatic amine (a2-s) comprises at least two primary aminogroups which each have one or two linear or branched alkyl groups havingfrom 1 to 12 carbon atoms, which may bear further functional groups, inthe a position. If one or more of Q², Q⁴, Q^(2′) and Q^(4′) are selectedso that they correspond to linear or branched alkyl groups which havefrom 1 to 12 carbon atoms and bear further functional groups, preferenceis given to amino groups and/or hydroxy groups and/or halogen atoms assuch functional groups.

The reduced reactivity brought about by the abovementioned alkyl groupsin the a position leads, in combination with the use of the component(a4) described in more detail below, to particularly stable gels havingparticularly good thermal conductivities in the ventilated state.

The alkyl groups as substituents Q in the general formula (I) arepreferably selected from among methyl, ethyl, n-propyl, isopropyl,n-butyl, sec-butyl and tert-butyl.

The amines (a2-s) are preferably selected from the group consisting of3,3′,5,5′-tetraalkyl-4,4′-diaminodiphenylmethane,3,3′,5,5′-tetraalkyl-2,2′-diaminodiphenylmethane and3,3′,5,5′-tetraalkyl-2,4′-diaminodiphenylmethane, where the alkyl groupsin the 3,3′,5 and 5′ positions can be identical or different and areeach selected independently from among linear or branched alkyl groupswhich have from 1 to 12 carbon atoms and can bear further functionalgroups. The abovementioned alkyl groups are preferably methyl, ethyl,n-propyl, i-propyl, n-butyl, sec-butyl or t-butyl (in each caseunsubstituted).

According to a further embodiment, the present invention therefore isdirected to the process for preparing a porous material as disclosedabove, wherein the amine component (a2) comprises at least one compoundselected from the group consisting of3,3′,5,5′-tetraalkyl-4,4′-diaminodiphenylmethane,3,3′,5,5′-tetraalkyl-2,2′-diaminodiphenylmethane and3,3′,5,5′-tetraalkyl-2,4′-diaminodiphenylmethane, where the alkyl groupsin the 3,3′,5 and 5′ positions can be identical or different and areselected independently from among linear or branched alkyl groups whichhave from 1 to 12 carbon atoms and can bear further functional groups.

In one embodiment, one, more than one or all hydrogen atoms of one ormore alkyl groups of the substituents Q can have been replaced byhalogen atoms, in particular chlorine. As an alternative, one, more thanone or all hydrogen atoms of one or more alkyl groups of thesubstituents Q can have been replaced by NH₂ or OH. However, the alkylgroups in the general formula (I) are preferably made up of carbon andhydrogen.

In a particularly preferred embodiment, component (a2) comprises3,3′,5,5′-tetraalkyl-4,4′-diaminodiphenylmethane, where the alkyl groupscan be identical or different and are each selected independently fromamong linear or branched alkyl groups which have from 1 to 12 carbonatoms and can optionally bear functional groups. The abovementionedalkyl groups are preferably selected from among unsubstituted alkylgroups, in particular methyl, ethyl, n-propyl, isopropyl, n-butyl,sec-butyl and tert-butyl, particularly preferably methyl and ethyl. Veryparticular preference is given to3,3′,5,5′-tetraethyl-4,4′-diaminodiphenylmethane and/or3,3′,5,5′-tetramethyl-4,4′-diaminodiphenylmethane.

The abovementioned polyfunctional amines of the type (a2-s) are knownper se to those skilled in the art or can be prepared by known methods.One of the known methods is the reaction of aniline or derivatives ofaniline with formaldehyde in the presence of an acid catalyst, inparticular the reaction of 2,4- or 2,6-dialkylaniline.

The component (a2) can optionally also comprise polyfunctional aromaticamines (a2-u) which differ from the amines of the structure (a2-s). Thearomatic amines (a2-u) preferably have exclusively aromatically boundamino groups, but can also have both (cyclo)aliphatically andaromatically bound reactive amino groups.

Suitable polyfunctional aromatic amines (a2-u) are, in particular,isomers and derivatives of diaminodiphenylmethane. Isomers andderivatives of diaminodiphenylmethane which are preferred asconstituents of component (a2) are, in particular,4,4′-diaminodiphenylmethane, 2,4′-diaminodiphenylmethane,2,2′-diaminodiphenylmethane and oligomeric diaminodiphenylmethane.

Further suitable polyfunctional aromatic amines (a2-u) are, inparticular, isomers and derivatives of toluenediamine. Isomers andderivatives of toluenediamine which are preferred as constituents ofcomponent (a2) are, in particular, toluene-2,4-diamine and/ortoluene-2,6-diamine and diethyltoluenediamines, in particular3,5-diethyltoluene-2,4-diamine and/or 3,5-diethyltoluene-2,6-diamine.

In a first, particularly preferred embodiment, component (a2) consistsexclusively of polyfunctional aromatic amines of the type (a2-s). In asecond preferred embodiment, component (a2) comprises polyfunctionalaromatic amines of the types (a2-s) and (a2-u). In the latter, secondpreferred embodiment, the component (a2) preferably comprises at leastone polyfunctional aromatic amine (a2-u), of which at least one isselected from among isomers and derivatives of diaminodiphenylmethane(MDA).

In the second preferred embodiment, component (a2) correspondinglyparticularly preferably comprises at least one polyfunctional aromaticamine (a2-u) selected from among 4,4′-diaminodiphenylmethane,2,4′-diaminodiphenylmethane, 2,2′-diaminodiphenylmethane and oligomericdiaminodiphenylmethane.

Oligomeric diaminodiphenylmethane comprises one or moremethylene-bridged condensation products of aniline and formaldehydehaving a plurality of rings. Oligomeric MDA comprises at least oneoligomer, but in general a plurality of oligomers, of MDA having afunctionality of more than 2, in particular 3 or 4 or 5. Oligomeric MDAis known or can be prepared by methods known per se. Oligomeric MDA isusually used in the form of mixtures with monomeric MDA.

The (average) functionality of a polyfunctional amine (a2-u) comprisingoligomeric MDA can vary in the range from about 2.3 to about 5, inparticular from 2.3 to 3.5 and in particular from 2.3 to 3. One suchmixture of MDA-based polyfunctional amines having differingfunctionalities is, in particular, crude MDA which is formed, inparticular, as intermediate in the condensation of aniline withformaldehyde, usually catalyzed by hydrochloric acid, in the productionof crude MDI.

In the abovementioned preferred second embodiment, particular preferenceis given to the component (a2) comprising oligomericdiaminodiphenylmethane as compound (a2-u) and having an overallfunctionality of at least 2.1.

The proportion of amines of type (a2-s) having the general formula (I)based on the total weight of all polyfunctional amines of the component(a2), which thus add up to a total of 100% by weight, is preferably from10 to 100% by weight, in particular from 30 to 100% by weight, veryparticularly preferably from 50 to 100% by weight, in particular from 80to 100% by weight.

The proportion of polyfunctional aromatic amines (a2-u) which differfrom the amines of type (a2-s) based on the total weight of allpolyfunctional amines of the component (a2) is preferably from 0 to 90%by weight, in particular from 0 to 70% by weight, particularlypreferably from 0 to 50% by weight, in particular from 0 to 20% byweight.

Component (a3)

Composition (A) can further comprise water as component (a3). If wateris used, the preferred amount of water used is at least 0.01% by weight,in particular at least 0.1% by weight, particularly preferably at least0.5% by weight, in particular at least 1% by weight. If water is used,the preferred amount of water used is at most 15% by weight, inparticular at most 13% by weight, particularly preferably at most 11% byweight, in particular at most 10% by weight, very particularlypreferably at most 9% by weight, in particular at most 8% by weight, ineach case based on the total weight of the composition (A), which is100% by weight. In a particularly preferred embodiment, water is notused.

According to a further embodiment, the present invention is directed tothe process for preparing a porous material as disclosed above, whereinno water is used.

According to an alternative further embodiment, the present invention isdirected to the process for preparing a porous material as disclosedabove, wherein at least 0.1% by weight of water is added.

A calculated content of amino groups can be derived from the watercontent and the content of reactive isocyanate groups of the component(a1) by assuming complete reaction of the water with the isocyanategroups of the component (a1) to form a corresponding number of aminogroups and adding this content to the content resulting from component(a2) (total n^(amine)). The resulting use ratio of the calculatedremaining NCO groups n^(NCO) to the amino groups calculated to have beenformed and used will hereinafter be referred to as calculated use ration^(NCO)/n^(amine) and is an equivalence ratio, i.e. a molar ratio of therespective functional groups.

Water reacts with the isocyanate groups to form amino groups andliberate CO₂. Polyfunctional amines are therefore partially produced asintermediate (in situ). In the further course of the reaction, they arereacted with isocyanate groups to form urea linkages. The production ofamines as intermediate leads to porous materials having particularlyhigh mechanical stability and low thermal conductivity. However, the CO₂formed must not disrupt gelling to such an extent that the structure ofthe resulting porous material is influenced in an undesirable way. Thisgives the abovementioned preferred upper limits for the water contentbased on the total weight of the composition (A).

In this case, the calculated use ratio (equivalence ratio)n^(NC)/n^(amine) is preferably from 1.01 to 5. The equivalence ratiomentioned is particularly preferably from 1.1 to 3, in particular from1.1 to 2. An excess of n^(NCO) over n^(amine) leads, in this embodiment,to lower shrinkage of the porous material, in particular xerogel, in theremoval of the solvent and as a result of synergistic interaction withthe catalyst (a4) to an improved network structure and to improved finalproperties of the resulting porous material.

The components (a0) to (a4) and if present (am) will hereinafter bereferred to collectively as organic gel precursor (A′). It will beobvious to a person skilled in the art that the partial reaction of thecomponent (a0) to (a4) and (am) leads to the actual gel precursor (A′)which is subsequently converted into a gel.

Catalyst (a4)

The composition (A) can further comprise at least one further catalystas component (a4). The amount of component (a4) used is preferably atleast 0.1% by weight, in particular at least 0.2% by weight,particularly preferably at least 0.5% by weight, in particular at least1% by weight. The amount of component (a4) used is preferably at most29.9% by weight, in particular at most 28% by weight, particularlypreferably at most 24% by weight, in particular at most 21% by weight,in each case based on the total weight of the composition (A).

Possible catalysts used as component (a4) are in principle all catalystsknown to those skilled in the art which accelerate the trimerization ofisocyanates (known as trimerization catalysts) and/or the reaction ofisocyanates with amino groups (known as gelling catalysts) and/or thereaction of isocyanates with water (known as blowing catalysts).

The corresponding catalysts are known per se and have different relativeactivities in respect of the abovementioned three reactions. Dependingon the relative activity, they can thus be assigned to one or more ofthe abovementioned types. Furthermore, it will be known to a personskilled in the art that reactions other than those mentioned above canalso occur.

Corresponding catalysts can be characterized, inter alia, according totheir gelling to blowing ratio, as is known, for example, fromPolyurethane, 3^(rd) edition, G. Oertel, Hanser Verlag, Munich, 1993.

According to a further embodiment, the present invention is directed tothe process for preparing a porous material as disclosed above, whereinthe catalyst catalyzes the trimerization to form isocyanurate groups.

According to another embodiment, the present invention is directed tothe process for preparing a porous material as disclosed above, whereincomponent (a4) comprises at least one tertiary amino group.

Preferred catalysts (a4) have a balanced gelling to blowing ratio, sothat the reaction of the component (a1) with water is not too stronglyaccelerated, leading to an adverse effect on the network structure, andat the same time results in a short gelling time so that the demoldingtime is advantageously short. Preferred catalysts at the same time havea significant activity in respect of trimerization. This favorablyinfluences the homogeneity of the network structure, resulting inparticularly advantageous mechanical properties.

The catalysts can be able to be incorporated as a monomer building block(incorporatable catalyst) or not be able to be incorporated.

Catalysts preferred as component (a4) are selected from the groupconsisting of primary, secondary and tertiary amines, triazinederivatives, urea derivatives, organic metal compounds, metal chelates,organophosphorus compounds, in particular oxides of phospholenes,quaternary ammonium salts, ammonium hydroxides and also alkali metal andalkaline earth metal hydroxides, alkoxides and carboxylates.

According to a further embodiment, the present invention thus isdirected to the process for preparing a porous material as disclosedabove, wherein component (a4) is selected from the group consisting ofprimary, secondary and tertiary amines, triazine derivatives,metal-organic compounds, metal chelates, oxides of phospholenes,quaternary ammonium salts, ammonium hydroxides and alkali metal andalkaline earth metal hydroxides, alkoxides and carboxylates.

Suitable organophosphorus compounds, in particular oxides ofphospholenes, are, for example, 1-methylphospholene oxide,3-methyl-1-phenylphospholene oxide, 1-phenylphospholene oxide,3-methyl-1-benzylphospholene oxide.

In the context of the present invention, for example those ureaderivatives are used which are known as catalysts for polyurethaneformation. Suitable urea-based compounds are urea and urea derivativessuch as for example, dimethyl urea, diphenyl urea, ethylene urea,propylene urea, dihydroxy ethylene urea.

The suitable catalysts (a4) are preferably trimerization catalysts.Suitable trimerization catalysts are in particular strong bases, forexample quaternary ammonium hydroxides such as tetraalkylammoniumhydroxides having from 1 to 4 carbon atoms in the alkyl radical andbenzyltrimethylammonium hydroxide, alkali metal hydroxides such aspotassium or sodium hydroxide and alkali metal alkoxides such as sodiummethoxide, potassium and sodium ethoxide and potassium isopropoxide.

Further suitable trimerization catalysts are, in particular, alkalimetal salts of carboxylic acids, e.g. potassium formate, sodium acetate,potassium acetate, caesium acetate, ammonium acetate, potassiumpropionate, potassium sorbate, potassium 2-ethylhexanoate, potassiumoctanoate, potassium trifluoroacetate, potassium trichloroacetate,sodium chloroacetate, sodium dichloroacetate, sodium trichloroacetate,potassium adipate, potassium benzoate, sodium benzoate, alkali metalsalts of saturated and unsaturated long-chain fatty acids having from 10to 20 carbon atoms, and optionally lateral OH groups

Further suitable trimerization catalysts are, in particular,N-hydroxyalkyl quaternary ammonium carboxylates, e.g.trimethylhydroxypropylammonium formate.

Further suitable trimerization catalysts are, in particular1-ethyl-3-methylimidazolium acetate (EMIM acetate) and1-butyl-3-methylimidazolium acetate (BMIM acetate),1-ethyl-3-methylimidazolium octanoate (EMIM octanoate) and1-butyl-3-methylimidazolium octanoate (BMIM octanoate).

Tertiary amines are also known per se to those skilled in the art astrimerization catalysts. Tertiary amines, i.e. compounds having at leastone tertiary amino group, are particularly preferred as catalysts (a4).Suitable tertiary amines having distinct properties as trimerizationcatalysts are, in particular,N,N′,N″-tris(dialkylaminoalkyl)-s-hexahydrotriazines, such asN,N′,N″-tris(dimethylaminopropyl)-s-hexahydrotriazine,tris(dimethylaminomethyl)phenol.

Metal-organic compounds are known per se as gel catalysts to a personskilled in the art. Tin-organic compounds such as tin 2-ethylhexanoateand dibutyltin dilaurate are particularly preferred.

Tertiary amines are also known per se as gel catalysts to a personskilled in the art. As mentioned above, tertiary amines are particularlypreferred as catalysts (a4). Suitable tertiary amines having goodproperties as gel catalysts are, in particular, N,N-dimethylbenzylamine,N,N′-dimethylpiperazine and N,N-dimethylcyclohexylamine,bis(2-dimethylaminoethyl) ether,N,N,N,N,N-pentamethyldiethylenetriamine, methylimidazole,dimethylimidazole, aminopropylimidazole, dimethylbenzylamine,1,6-diazabicyclo[5.4.0]undec-7-ene, triethylamine, triethylenediamine(1,4-diazabicyclo[2.2.2]octane), dimethylaminoethanolamine,dimethylaminopropylamine, N,N-dimethylaminoethoxyethanol,N,N,N-trimethylaminoethylethanolamine, triethanolamine, diethanolamine,triisopropanolamine, diisopropanolamine, methyldiethanolamine andbutyldiethanolamine.

Catalysts which are particularly preferred as component (a4) areselected from the group consisting of dimethylcyclohexylamine,dimethylpiperazine, bis(2-dimethylaminoethyl) ether,N,N,N,N,N-pentamethyldiethylenetriamine, methylimidazole,dimethylimidazole, aminopropylimidazole, dimethylbenzylamine,1,6-diazabicyclo[5.4.0]undec-7-ene,trisdimethylaminopropylhexahydrotriazine, triethylamine,tris(dimethylaminomethyl)phenol, triethylenediamine(diazabicyclo[2.2.2]octane), dimethylaminoethanolamine,dimethylaminopropylamine, N,N-dimethylaminoethoxyethanol,N,N,N-trimethylaminoethylethanolamine, triethanolamine, diethanolamine,triisopropanolamine, diisopropanolamine, methyldiethanolamine,butyldiethanolamine.

Very particular preference is given to dimethylcyclohexylamine,dimethylpiperazine, methylimidazole, dimethylimidazole,dimethylbenzylamine, 1,6-diazabicyclo[5.4.0]undec-7-ene,trisdimethylaminopropylhexahydrotriazine, triethylamine,tris(dimethylaminomethyl)phenol, triethylenediamine(diazabicyclo[2.2.2]octane), dimethylaminoethanolamine,dimethylaminopropylamine, N,N,N-trimethylaminoethylethanolamine,triethanolamine, diethanolamine, methyldiethanolamine,butyldiethanolamine, metal acetylacetonates, ammonium ethylhexanoates,metal acetates, propionates, sorbates, ethylhexanoates, octanoates andbenzoates.

Therefore, according to a further embodiment, the present invention isdirected to the process for preparing a porous material as disclosedabove, wherein component (a4) is selected from the group consisting ofdimethylcyclohexylamine, bis(2-dimethylaminoethyl) ether,N,N,N,N,N-pentamethyldiethylenetriamine, methylimidazole,dimethylimidazole, aminopropylimidazole, dimethylbenzylamine,1,6-diazabicyclo[5.4.0]undec-7-ene,trisdimethylaminopropylhexahydrotriazine, triethylamine,tris(dimethylaminomethyl)phenol, triethylenediamine(diazabicyclo[2.2.2]octane), dimethylaminoethanolamine,dimethylaminopropylamine, N,N-dimethylaminoethoxyethanol,N,N,N-trimethylaminoethylethanolamine, triethanolamine, diethanolamine,triisopropanolamine, diisopropanolamine, methyldiethanolamine,butyldiethanolamine, metal acetylacetonates, ammonium ethylhexanoatesand metal acetates, propionates, sorbates, ethylhexanoates, octanoatesand benzoates.

According to the present invention, it is possible to use the catalystas such in the process of the invention. It is also possible to use thecatalyst in form of a solution. Furthermore, the catalyst (a4) can becombined with catalyst system (CS).

Solvent (B)

According to the present invention, the reaction takes place in thepresence of a solvent (B).

For the purposes of the present invention, the term solvent (B)comprises liquid diluents, i.e. both solvents in the narrower sense andalso dispersion media. The mixture can, in particular, be a truesolution, a colloidal solution or a dispersion, e.g. an emulsion orsuspension. The mixture is preferably a true solution. The solvent (B)is a compound which is liquid under the conditions of step (a),preferably an organic solvent.

The solvent (B) can in principle be any suitable compound or mixture ofa plurality of compounds, with the solvent (B) being liquid under thetemperature and pressure conditions under which the mixture is providedin step (a) (dissolution conditions for short). The composition of thesolvent (B) is selected so that it is able to dissolve or disperse,preferably dissolve, the organic gel precursor. Preferred solvents (B)are those which are a solvent for the components (a1) to (a4), i.e. oneswhich dissolve the components (a1) to (a4) completely under the reactionconditions.

The reaction product of the reaction in the presence of the solvent (B)is initially a gel, i.e. a viscoelastic chemical network which isswollen by the solvent (B). A solvent (B) which is a good swelling agentfor the network formed in step (b) generally leads to a network havingfine pores and a small average pore diameter, while a solvent (B) whichis a poor swelling agent for the gel resulting from step (b) generallyleads to a coarse-pored network having a large average pore diameter.

The choice of the solvent (B) thus influences the desired pore sizedistribution and the desired porosity. The choice of the solvent (B) isalso generally made in such a way that precipitation or flocculation dueto formation of a precipitated reaction product does not occur to asignificant extent during or after step (b) of the process of theinvention.

When a suitable solvent (B) is chosen, the proportion of precipitatedreaction product is usually less than 1% by weight, based on the totalweight of the mixture. The amount of precipitated product formed in aparticular solvent (B) can be determined gravimetrically by filteringthe reaction mixture through a suitable filter before the gelling point.

Possible solvents (B) are solvents known from the prior art forisocyanate-based polymers. Preferred solvents are those which are asolvent for the components (a1) to (a4), i.e. solvents which dissolvethe constituents of the components (a1) to (a4) virtually completelyunder the reaction conditions. The solvent (B) is preferably inert, i.e.unreactive, toward component (a1). Furthermore, solvent (B) preferablyis miscible with monool (am).

Possible solvents (B) are, for example, ketones, aldehydes, alkylalkanoates, amides such as formamide, N-methylpyrollidone,N-ethylpyrollidone, sulfoxides such as dimethyl sulfoxide, aliphatic andcycloaliphatic halogenated hydrocarbons, halogenated aromatic compoundsand fluorine-containing ethers. Mixtures of two or more of theabovementioned compounds are likewise possible.

Further possibilities as solvents (B) are acetals, in particulardiethoxymethane, dimethoxymethane and 1,3-dioxolane.

Dialkyl ethers and cyclic ethers are likewise suitable as solvent (B).Preferred dialkyl ethers are, in particular, those having from 2 to 6carbon atoms, in particular methyl ethyl ether, diethyl ether, methylpropyl ether, methyl isopropyl ether, propyl ethyl ether, ethylisopropyl ether, dipropyl ether, propyl isopropyl ether, diisopropylether, methyl butyl ether, methyl isobutyl ether, methyl t-butyl ether,ethyl n-butyl ether, ethyl isobutyl ether and ethyl t-butyl ether.Preferred cyclic ethers are, in particular, tetrahydrofuran, dioxane andtetrahydropyran.

Aldehydes and/or ketones are particularly preferred as solvent (B).Aldehydes or ketones suitable as solvent (B) are, in particular, thosecorresponding to the general formula R²—(CO)—R¹, where R¹ and R² areeach hydrogen or an alkyl group having 1, 2, 3, 4, 5, 6 or 7 carbonatoms. Suitable aldehydes or ketones are, in particular, acetaldehyde,propionaldehyde, nbutyraldehyde, isobutyraldehyde, 2-ethylbutyraldehyde,valeraldehyde, isopentaldehyde, 2-methylpentaldehyde,2-ethylhexaldehyde, acrolein, methacrolein, crotonaldehyde, furfural,acrolein dimer, methacrolein dimer, 1,2,3,6-tetrahydrobenzaldehyde,6-methyl-3-cyclohexenaldehyde, cyanoacetaldehyde, ethyl glyoxylate,benzaldehyde, acetone, diethyl ketone, methyl ethyl ketone, methylisobutyl ketone, methyl n-butyl ketone, methyl pentylketone, dipropylketone, ethyl isopropyl ketone, ethyl butyl ketone, diisobutylketone,5-methyl-2-acetyl furan, 2-acetylfuran, 2-methoxy-4-methylpentan-2-one,5-methylheptan-3-one, 2-heptanone, octanone, cyclohexanone,cyclopentanone, and acetophenone. The abovementioned aldehydes andketones can also be used in the form of mixtures. Ketones and aldehydeshaving alkyl groups having up to 3 carbon atoms per substituent arepreferred as solvent (B).

Further preferred solvents are alkyl alkanoates, in particular methylformate, methyl acetate, ethyl formate, isopropyl acetate, butylacetate, ethyl acetate, glycerine triacetate and ethyl acetoacetate.Preferred halogenated solvents are described in WO 00/24799, page 4,line 12 to page 5, line 4.

Further suitable solvents (B) are organic carbonates such as for exampledimethyl carbonate, diethyl carbonate, ethylene carbonate, propylenecarbonate or butylene carbonate.

In many cases, particularly suitable solvents (B) are obtained by usingtwo or more completely miscible compounds selected from theabovementioned solvents.

To obtain a sufficiently stable gel which does not shrink too muchduring drying in step (c) in step (b), the proportion of the composition(A) based on the total weight of the mixture (I) comprising composition(A) and the solvent (B), which is 100% by weight, must generally be notless than 5% by weight. The proportion of the composition (A) based onthe total weight of the mixture (I) comprising composition (A) and thesolvent (B), which is 100% by weight, is preferably at least 6% byweight, particularly preferably at least 8% by weight, in particular atleast 10% by weight.

On the other hand, the concentration of the composition (A) in themixture provided must not be too high since otherwise no porous materialhaving favorable properties is obtained. In general, the proportion ofthe composition (A) based on the total weight of the mixture (I)comprising composition (A) and the solvent (B), which is 100% by weight,is not more than 40% by weight. The proportion of the composition (A)based on the total weight of the mixture (I) comprising composition (A)and the solvent (B), which is 100% by weight, is preferably not morethan 35% by weight, particularly preferably not more than 25% by weight,in particular not more than 20% by weight.

The total proportion by weight of the composition (A) based on the totalweight of the mixture (I) comprising composition (A) and the solvent(B), which is 100% by weight, is preferably from 8 to 25% by weight, inparticular from 10 to 20% by weight, particularly preferably from 12 to18% by weight. Adherence to the amount of the starting materials in therange mentioned leads to porous materials having a particularlyadvantageous pore structure, low thermal conductivity and low shrinkingduring drying.

Before the reaction, it is necessary to mix the components used, inparticular to mix them homogeneously. The rate of mixing should be highrelative to the rate of the reaction in order to avoid mixing defects.Appropriate mixing methods are known per se to those skilled in the art.

According to the present invention, a solvent (B) is used. The solvent(B) can also be a mixture of two or more solvents, for example three orfour solvents. Suitable solvents are for example mixtures of two or moreketones, for example mixtures of acetone and diethyl ketone, mixtures ofacetone and methyl ethyl ketone or mixtures of diethyl ketone and methylethyl ketone.

Further preferred solvents are mixtures of propylene carbonate with oneor more solvents, for example mixtures of propylene carbonate anddiethyl ketone, or mixtures of propylene carbonate with two or moreketones, for example mixtures of propylene carbonate with acetone anddiethyl ketone, mixtures of propylene carbonate with acetone and methylethyl ketone or mixtures of propylene carbonate with diethyl ketone andmethyl ethyl ketone.

Preferred Process for Producing the Porous Materials

The process of the invention comprises at least the following steps:

-   (a) provision of the mixture comprising the composition (A) and the    solvent (B) as described above,-   (b) reaction of the components in composition (A) in the presence of    the solvent (B) to form a gel and-   (c) drying of the gel obtained in the preceding step.

Preferred embodiments of steps (a) to (c) will be described in detailbelow.

Step (a)

According to the invention, a mixture comprising composition (A) and thesolvent (B) are provided in step (a).

The components of composition (A), for example the components (a1) and(a2) are preferably provided separately from one another, each in asuitable partial amount of the solvent (B). The separate provision makesit possible for the gelling reaction to be optimally monitored orcontrolled before and during mixing.

Component (a0) or composition (CS), optionally (am), (a3) and (a4) areparticularly preferably provided as a mixture with component (a2), i.e.separately from component (a1).

The mixture or mixtures provided in step (a) can also comprise customaryauxiliaries known to those skilled in the art as further constituents.Mention may be made by way of example of surface-active substances,flame retardants, nucleating agents, opacifiers, oxidation stabilizers,lubricants and mold release agents, dyes and pigments, stabilizers, e.g.against hydrolysis, light, heat or discoloration, inorganic and/ororganic fillers, reinforcing materials and biocides.

Further information regarding the abovementioned auxiliaries andadditives may be found in the specialist literature, e.g. in PlasticsAdditive Handbook, 5th edition, H. Zweifel, ed. Hanser Publishers,Munich, 2001.

Step (b)

According to the invention, the reaction of the components ofcomposition (A) takes place in the presence of the solvent (B) to form agel in step (b). To carry out the reaction, a homogeneous mixture of thecomponents provided in step (a) firstly has to be produced.

The provision of the components provided in step (a) can be carried outin a conventional way.

A stirrer or another mixing device is preferably used here in order toachieve good and rapid mixing. The time required for producing thehomogeneous mixture should be short in relation to the time during whichthe gelling reaction leads to at least partial formation of a gel, inorder to avoid mixing defects. The other mixing conditions are generallynot critical; for example, mixing can be carried out at from 0 to 100°C. and from 0.1 to 10 bar (absolute), in particular at, for example,room temperature and atmospheric pressure. After a homogeneous mixturehas been produced, the mixing apparatus is preferably switched off.

The gelling reaction is a polyaddition reaction, in particular apolyaddition of isocyanate groups and amino groups.

For the purposes of the present invention, a gel is a crosslinked systembased on a polymer which is present in contact with a liquid (known assolvogel or lyogel, or with water as liquid: aquagel or hydrogel). Here,the polymer phase forms a continuous three-dimensional network.

In step (b) of the process of the invention, the gel is usually formedby allowing to rest, e.g. by simply allowing the container, reactionvessel or reactor in which the mixture is present (hereinafter referredto as gelling apparatus) to stand. The mixture is preferably no longerstirred or mixed during gelling (gel formation) because this couldhinder formation of the gel. It has been found to be advantageous tocover the mixture during gelling or to close the gelling apparatus.

Gelling is known per se to a person skilled in the art and is described,for example, in WO 2009/027310 on page 21, line 19 to page 23, line 13.

Step (c)

According to the invention, the gel obtained in the previous step isdried in step (c).

Drying under supercritical conditions is in principle possible,preferably after replacement of the solvent by CO₂ or other solventssuitable for the purposes of supercritical drying. Such drying is knownper se to a person skilled in the art. Supercritical conditionscharacterize a temperature and a pressure at which CO₂ or any solventused for removal of the gelation solvent is present in the supercriticalstate. In this way, shrinkage of the gel body on removal of the solventcan be reduced.

However, in view of the simple process conditions, preference is givento drying the gels obtained by conversion of the liquid comprised in thegel into the gaseous state at a temperature and a pressure below thecritical temperature and the critical pressure of the liquid comprisedin the gel.

The drying of the gel obtained is preferably carried out by convertingthe solvent (B) into the gaseous state at a temperature and a pressurebelow the critical temperature and the critical pressure of the solvent(B). Accordingly, drying is preferably carried out by removing thesolvent (B) which was present in the reaction without prior replacementby a further solvent.

Such methods are likewise known to those skilled in the art and aredescribed in WO 2009/027310 on page 26, line 22 to page 28, line 36.

According to a further embodiment, the present invention is directed tothe process for preparing a porous material as disclosed above, whereinthe drying according to step c) is carried out by converting the liquidcomprised in the gel into the gaseous state at a temperature and apressure below the critical temperature and the critical pressure of theliquid comprised in the gel.

According to a further embodiment, the present invention is directed tothe process for preparing a porous material as disclosed above, whereinthe drying according to step c) is carried out under supercriticalconditions.

Properties of the Porous Materials and Use

The present invention further provides the porous materials which can beobtained by the process of the invention. Aerogels are preferred asporous materials for the purposes of the present invention, i.e. theporous material which can be obtained according to the invention ispreferably an aerogel.

Furthermore, the present invention therefore is directed to a porousmaterial which is obtained or obtainable by the process for preparing aporous material as disclosed above. In particular, the present inventionis directed to a porous material which is obtained or obtainable by theprocess for preparing a porous material as disclosed above, wherein thedrying according to step c) is carried out under supercriticalconditions.

The average pore diameter is determined by scanning electron microscopyand subsequent image analysis using a statistically significant numberof pores. Corresponding methods are known to those skilled in the art.

The volume average pore diameter of the porous material is preferablynot more than 4 microns. The volume average pore diameter of the porousmaterial is particularly preferably not more than 3 microns, veryparticularly preferably not more than 2 microns and in particular notmore than 1 micron.

Although a very small pore size combined with a high porosity isdesirable from the point of view of a low thermal conductivity, from thepoint of view of production and to obtain a sufficiently mechanicallystable porous material, there is a practical lower limit to the volumeaverage pore diameter. In general, the volume average pore diameter isat least 20 nm, preferably at least 50 nm.

The porous material which can be obtained according to the inventionpreferably has a porosity of at least 70% by volume, in particular from70 to 99% by volume, particularly preferably at least 80% by volume,very particularly preferably at least 85% by volume, in particular from85 to 95% by volume. The porosity in % by volume means that thespecified proportion of the total volume of the porous materialcomprises pores. Although a very high porosity is usually desirable fromthe point of view of a minimal thermal conductivity, an upper limit isimposed on the porosity by the mechanical properties and theprocessability of the porous material.

The components of composition (A), for example the components (a0) to(a3) and optionally (am) and (a4), as long as the catalyst can beincorporated, are present in reactive (polymer) form in the porousmaterial which can be obtained according to the invention. Owing to thecomposition according to the invention, the monomer building blocks (a1)and (a2) are predominantly bound via urea linkages and/or viaisocyanurate linkages in the porous material, with the isocyanurategroups being formed by trimerization of isocyanate groups of the monomerbuilding blocks (a1). If the porous material comprises furthercomponents, further possible linkages are, for example, urethane groupsformed by reaction of isocyanate groups with alcohols or phenols.

The determination of the mol % of the linkages of the monomer buildingblocks in the porous material is carried out by means of NMRspectroscopy (nuclear magnetic resonance) in the solid or in the swollenstate. Suitable methods of determination are known to those skilled inthe art.

The density of the porous material which can be obtained according tothe invention is usually from 20 to 600 g/l, preferably from 50 to 500g/I and particularly preferably from 70 to 200 g/l.

The process of the invention gives a coherent porous material and notonly a polymer powder or particles. Here, the three-dimensional shape ofthe resulting porous material is determined by the shape of the gelwhich is in turn determined by the shape of the gelling apparatus. Thus,for example, a cylindrical gelling vessel usually gives an approximatelycylindrical gel which can then be dried to give a porous material havinga cylindrical shape.

The porous materials which can be obtained according to the inventionhave a low thermal conductivity, a high porosity and a low densitycombined with high mechanical stability. In addition, the porousmaterials have a small average pore size. The combination of theabovementioned properties allows the materials to be used as insulationmaterial in the field of thermal insulation, in particular forapplications in the ventilated state as building materials.

The porous materials which can be obtained according to the inventionhave advantageous thermal properties and also further advantageousproperties such as simple processability and high mechanical stability,for example low brittleness.

In comparison to materials known from the state of the art, the porousmaterials according to the present invention have a reduced density andimproved compressive strength.

The present invention is also directed to the use of porous materials asdisclosed above or a porous material obtained or obtainable according toa process as disclosed above as thermal insulation material or forvacuum insulation panels. The thermal insulation material is for exampleinsulation material which is used for insulation in the interior or theexterior of a building. The porous material according to the presentinvention can advantageously be used in thermal insulation systems suchas for example composite materials.

According to a further embodiment, the present invention therefore isdirected to the use of porous materials as disclosed above, wherein theporous material is used in interior or exterior thermal insulationsystems. According to a further embodiment, the present invention isalso directed to the use of porous materials as disclosed above, whereinthe porous material is used in water tank or ice maker thermalinsulation systems.

The present invention includes the following embodiments, wherein theseinclude the specific combinations of embodiments as indicated by therespective interdependencies defined therein.

-   1. Process for preparing a porous material, at least comprising the    steps of:    -   a) providing a mixture (I) comprising        -   (i) a composition (A) comprising components suitable to form            an organic gel and        -   (ii) a solvent (B),    -   b) reacting the components in the composition (A) in the        presence of the solvent (B) to form a gel, and    -   c) drying of the gel obtained in step b),    -   wherein the composition (A) comprises a catalyst system (CS)        comprising        -   a catalyst component (C1) selected from the group consisting            of alkali metal and earth alkali metal, ammonium, ionic            liquid salts of a saturated or unsaturated monocarboxylic            acid and        -   a carboxylic acid as catalyst component (C2).-   2. The process according to embodiment 1, wherein the catalyst    component (C1) is selected from the group consisting of alkali metal    and earth alkali metal, ammonium, ionic liquid salts of a saturated    or unsaturated monocarboxylic acid with 2 to 8 carbon atoms.-   3. The process according to any of embodiments 1 or 2, wherein the    catalyst component (C2) is selected from the group of saturated or    unsaturated monocarboxylic acids with 2 to 12 carbon atoms.-   4. The process according to embodiment 1, wherein the catalyst    component (C1) is selected from the group consisting of alkali metal    and earth alkali metal salts of a saturated or unsaturated    monocarboxylic acid with 2 to 8 carbon atoms and wherein the    catalyst component (C2) is selected from the group of saturated or    unsaturated monocarboxylic acids with 2 to 12 carbon atoms.-   5. The process according to any of embodiments 1 or 2, wherein the    catalyst system (CS) is present in the composition (A) in an amount    in the range of from 0.1 to 30% by weight, based on the total weight    of the composition (A).-   6. The process according to any of embodiments 4 or 5, wherein the    catalyst system (CS) comprises catalyst components (C1) and (C2) in    a ratio in the range of from 1:10 to 10:1.-   7. The process according to any of embodiments 1 to 6, wherein the    composition (A) comprises at least one monool (am).-   8. The process according to any of embodiments 1 to 7, wherein the    composition (A) comprises at least one polyfunctional isocyanate as    component (a1).-   9. The process according to any of embodiments 1 or 8, wherein the    composition (A) comprises at least one polyfunctional isocyanate as    component (a1), and at least one aromatic amine as component (a2),    optionally comprises water as component (a3), and optionally    comprises at least one further catalyst as component (a4).-   10. The process according to embodiment 9, wherein the at least one    aromatic amine is a polyfunctional aromatic amine.-   11. The process according to any of embodiments 9 or 10, wherein the    at least one aromatic amine (a2) has the general formula I

-   -   where R¹ and R² can be identical or different and are each        selected independently from among hydrogen and linear or        branched alkyl groups having from 1 to 6 carbon atoms and all        substituents Q¹ to Q⁵ and Q^(1′) to Q^(5′) are identical or        different and are each selected independently from among        hydrogen, a primary amino group and a linear or branched alkyl        group having from 1 to 12 carbon atoms, where the alkyl group        can bear further functional groups, with the proviso that the        compound having the general formula I comprises at least two        primary amino groups, where at least one of Q¹, Q³ and Q⁵ is a        primary amino group and at least one of Q^(1′), Q^(3′) and        Q^(5′) is a primary amino group.

-   12. The process according to any of embodiments 1 to 11, wherein    composition (A) comprises    -   (a0) from 0.1 to 30% by weight of catalyst system (CS),    -   (a1) from 25 to 94.9% by weight of at least one polyfunctional        isocyanate, and    -   (a2) from 0.1 to 30% by weight of at least one polyfunctional        aromatic amine having the general formula I

-   -   -   where R¹ and R² can be identical or different and are each            selected independently from among hydrogen and linear or            branched alkyl groups having from 1 to 6 carbon atoms and            all substituents Q¹ to Q⁵ and Q^(1′) to Q^(5′) are identical            or different and are each selected independently from among            hydrogen, a primary amino group and a linear or branched            alkyl group having from 1 to 12 carbon atoms, where the            alkyl group can bear further functional groups, with the            proviso that the compound having the general formula I            comprises at least two primary amino groups, where at least            one of Q¹, Q³ and Q⁵ is a primary amino group and at least            one of Q^(1′), Q^(3′) and Q^(5′) is a primary amino group,

    -   (a3) from 0 to 15% by weight of water, and

    -   (a4) from 0 to 29.9% by weight of at least one further catalyst,

    -   in each case based on the total weight of the components (a0) to        (a4), where the % by weight of the components (a0) to (a4) adds        up to 100% by weight and

    -   wherein the sum of the components (a0) and (a4) is in the range        of from 0.1 to 30% by weight based on the total weight of the        components (a0) to (a4).

-   13. The process according to any of embodiments 9 to 12, wherein the    amine component (a2) comprises at least one compound selected from    the group consisting of    3,3′,5,5′-tetraalkyl-4,4′-diaminodiphenylmethane,    3,3′,5,5′-tetraalkyl-2,2′-diaminodiphenylmethane and    3,3′,5,5′-tetraalkyl-2,4′-diaminodiphenylmethane, where the alkyl    groups in the 3,3′,5 and 5′ positions can be identical or different    and are selected independently from among linear or branched alkyl    groups which have from 1 to 12 carbon atoms and can bear further    functional groups.

-   14. The process according to any of embodiments 8 to 13, wherein    component (a4) catalyzes the trimerization to form isocyanurate    groups.

-   15. The process according to any of embodiments 9 to 14, wherein    component (a4) comprises at least one tertiary amino group.

-   16. The process according to any of embodiments 1 to 15, wherein no    water is used.

-   17. The process according to any of embodiments 1 to 16, wherein the    drying according to step c) is carried out by converting the liquid    comprised in the gel into the gaseous state at a temperature and a    pressure below the critical temperature and the critical pressure of    the liquid comprised in the gel.

-   18. The process according to any of embodiments 1 to 16, wherein the    drying according to step c) is carried out under supercritical    conditions.

-   19. A porous material, which is obtained or obtainable by the    process according to any of embodiments 1 to 18.

-   20. The use of porous materials according to embodiment 19 or a    porous material obtained or obtainable by the process according to    any of embodiments 1 to 18 as thermal insulation material or for    vacuum insulation panels.

-   21. The use according to embodiment 20, wherein the porous material    is used in interior or exterior thermal insulation systems.

-   22. The use according to embodiment 20, wherein the porous material    is used in water tank or ice maker thermal insulation systems.

Examples will be used below to illustrate the invention.

EXAMPLES 1. Methods

1.1 Determination of Thermal Conductivity

The thermal conductivity was measured according to DIN EN 12667 with aheat flow meter from Hesto (Lambda Control A50).

1.2 Solvent Extraction with Supercritical Carbon Dioxide

One or several gel monoliths were placed onto sample trays in anautoclave of 25 l volume. Subsequent to filling with supercriticalcarbon dioxide (scCO₂), the gelation solvent was removed (drying) byflowing scCO₂ through the autoclave for 24 h (20 kg/h). Process pressurewas kept between 120 and 130 bar and process temperature at 45° C. inorder to maintain carbon dioxide in a supercritical state.

At the end of the process, the pressure was reduced to normalatmospheric pressure in a controlled manner while maintaining the systemat a temperature of 45° C. The autoclave was opened, and the obtainedporous monoliths were removed.

1.3 Determination of Compressive Strength and E Modulus

The compressive strength and the elastic modulus were measured accordingto DIN 53421 with 10% strain.

2. Materials

-   -   Component a1: oligomeric MDI (Lupranat M200) having an NCO        content of 30.9 g per 100 g accordance with ASTM D-5155-96 A, a        functionality in the region of three and a viscosity of 2100        mPa·s at 25° C. in accordance with DIN 53018 (hereafter “M200”)    -   Component a2: 3,3′,5,5′-Tetraethyl-4,4′diaminodiphenylmethane        (hereinafter “MDEA”)    -   Catalysts: Dabco K15 (potassium ethylhexanoate dissolved in        diethylene glycol (85%))        -   Potassium sorbate dissolved in monoethylene glycol (20%)        -   Potassium acetate dissolved in tetraethylene glycol (20%)        -   Potassium benzoate dissolved in monoethylene glycol (20%)        -   Butyldiethanolamin    -   Carboxylic acids: Propionic acid        -   Acetic acid

3. Examples

Thermal conductivity values for all examples are shown in Table 1.Furthermore, data regarding the compressive strength and density areincluded for several examples.

3.1 Example 1 (Comparative)

In a polypropylene container, 48 g M200 were stirred in 220 g MEK at 20°C. leading to a clear solution. Similarly, 8 g MDEA, 1 g Ksorbatesolution were dissolved in 220 g MEK to obtain a second solution. Thesolutions were combined in a rectangular container (20×20 cm×5 cmheight) by pouring one solution into the other, which led to ahomogeneous mixture of low viscosity. The container was closed with alid and the mixture was gelled at room temperature for 24 h. Theresulting monolithic gel slab was dried through solvent extraction withscCO₂ in a 25 l autoclave leading to a porous material.

The compressive strength was determined according to DIN 53421 with 10%strain.

The elastic modulus was 6.68 N/mm².

3.2 Example 2

In a polypropylene container, 48 g M200 were stirred in 220 g MEK at 20°C. leading to a clear solution. Similarly, 8 g MDEA, 1 g Ksorbatesolution and 0.8 g acetic acid were dissolved in 220 g MEK to obtain asecond solution. The solutions were combined in a rectangular container(20×20 cm×5 cm height) by pouring one solution into the other, which ledto a homogeneous mixture of low viscosity. The container was closed witha lid and the mixture was gelled at room temperature for 24 h. Theresulting monolithic gel slab was dried through solvent extraction withscCO₂ in a 25 l autoclave leading to a porous material.

The compressive strength was determined according to DIN 53421 with 10%strain.

The elastic modulus was 9.56 N/mm².

3.3 Example 3 (Comparative)

In a polypropylene container, 48 g M200 were stirred in 220 g MEK at 20°C. leading to a clear solution. Similarly, 8 g MDEA, 1 g Ksorbatesolution and 6 g butanol were dissolved in 220 g MEK to obtain a secondsolution. The solutions were combined in a rectangular container (20×20cm×5 cm height) by pouring one solution into the other, which led to ahomogeneous mixture of low viscosity. The container was closed with alid and the mixture was gelled at room temperature for 24 h. Theresulting monolithic gel slab was dried through solvent extraction withscCO₂ in a 25 l autoclave leading to a porous material.

The compressive strength was determined according to DIN 53421 with 10%strain.

The elastic modulus was 8.32 N/mm².

3.4 Example 4

In a polypropylene container, 48 g M200 were stirred in 220 g MEK at 20°C. leading to a clear solution. Similarly, 8 g MDEA, 1 g Ksorbatesolution, 6 g butanol and 1 g propionic acid were dissolved in 220 g MEKto obtain a second solution. The solutions were combined in arectangular container (20×20 cm×5 cm height) by pouring one solutioninto the other, which led to a homogeneous mixture of low viscosity. Thecontainer was closed with a lid and the mixture was gelled at roomtemperature for 24 h. The resulting monolithic gel slab was driedthrough solvent extraction with scCO₂ in a 25 l autoclave leading to aporous material.

The compressive strength was determined according to DIN 53421 with 10%strain.

The elastic modulus was 8.55 N/mm².

3.5 Example 5

In a polypropylene container, 48 g M200 were stirred in 220 g MEK at 20°C. leading to a clear solution. Similarly, 8 g MDEA, 1 g Ksorbatesolution, 4 g BDeoA, 6 g butanol and 1 g propionic acid were dissolvedin 220 g MEK to obtain a second solution. The solutions were combined ina rectangular container (20×20 cm×5 cm height) by pouring one solutioninto the other, which led to a homogeneous mixture of low viscosity. Thecontainer was closed with a lid and the mixture was gelled at roomtemperature for 24 h. The resulting monolithic gel slab was driedthrough solvent extraction with scCO₂ in a 25 l autoclave leading to aporous material.

The compressive strength was determined according to DIN 53421 with 10%strain.

The elastic modulus was 14.52 N/mm².

3.6 Example 6 (Comparative)

In a polypropylene container, 48 g M200 were stirred in 220 g MEK at 20°C. leading to a clear solution. Similarly, 8 g MDEA, 4 g Kacetatesolution and 4 g water were dissolved in 220 g MEK to obtain a secondsolution. The solutions were combined in a rectangular container (20×20cm×5 cm height) by pouring one solution into the other, which led tosedimentation of undissolved particles.

3.7 Example 7

In a polypropylene container, 48 g M200 were stirred in 220 g MEK at 20°C. leading to a clear solution. Similarly, 8 g MDEA, 4 g Kacetatesolution and 4 g water and 1 g acetic acid were dissolved in 220 g MEKto obtain a second solution. The solutions were combined in arectangular container (20×20 cm×5 cm height) by pouring one solutioninto the other, which led to a homogeneous mixture of low viscosity. Thecontainer was closed with a lid and the mixture was gelled at roomtemperature for 24 h. The resulting monolithic gel slab was driedthrough solvent extraction with scCO₂ in a 25 l autoclave leading to aporous material.

The compressive strength was determined according to DIN 53421 with 10%strain.

The elastic modulus was 13.59 N/mm².

3.8 Example 8

In a polypropylene container, 48 g M200 were stirred in 220 g MEK at 20°C. leading to a clear solution. Similarly, 8 g MDEA, 1 g Kacetatesolution and 1 g acetic acid were dissolved in 220 g MEK to obtain asecond solution. The solutions were combined in a rectangular container(20×20 cm×5 cm height) by pouring one solution into the other, which ledto a homogeneous mixture of low viscosity. The container was closed witha lid and the mixture was gelled at room temperature for 24 h. Theresulting monolithic gel slab was dried through solvent extraction withscCO₂ in a 25 l autoclave leading to a porous material.

The compressive strength was determined according to DIN 53421 with 10%strain.

The elastic modulus was 13.80 N/mm².

3.9 Example 9 (comparative)

In a polypropylene container, 48 g M200 were stirred in 220 g MEK at 20°C. leading to a clear solution. Similarly, 8 g MDEA, 1 g K15 weredissolved in 220 g MEK to obtain a second solution. The solutions werecombined in a rectangular container (20×20 cm×5 cm height) by pouringone solution into the other, which led to a homogeneous mixture of lowviscosity. The container was closed with a lid and the mixture wasgelled at room temperature for 24 h. The resulting monolithic gel slabwas broken upon handling and subsequently not supercritically dried.

3.10 Example 10

In a polypropylene container, 48 g M200 were stirred in 220 g MEK at 20°C. leading to a clear solution. Similarly, 8 g MDEA, 1 g K15 and 1 gpropionic acid were dissolved in 220 g MEK to obtain a second solution.The solutions were combined in a rectangular container (20×20 cm×5 cmheight) by pouring one solution into the other, which led to ahomogeneous mixture of low viscosity. The container was closed with alid and the mixture was gelled at room temperature for 24 h. Theresulting monolithic gel slab was dried through solvent extraction withscCO₂ in a 25 l autoclave leading to a porous material.

The compressive strength was determined according to DIN EN ISO 844 with6.6% strain.

The elastic modulus was 16.52 N/mm².

3.11 Example 11 (Comparative)

In a polypropylene container, 48 g M200 were stirred in 220 g MEK at 20°C. leading to a clear solution. Similarly, 8 g MDEA, 4 g Kbenzoatesolution were dissolved in 220 g MEK to obtain a second solution. Thesolutions were combined in a rectangular container (20×20 cm×5 cmheight) by pouring one solution into the other, which led to ahomogeneous mixture of low viscosity. The container was closed with alid and the mixture was gelled at room temperature for 24 h. Theresulting monolithic gel slab was dried through solvent extraction withscCO₂ in a 25 l autoclave leading to a porous material.

The compressive strength was determined according to DIN EN ISO 844 with5.7% strain.

The elastic modulus was 16.63 N/mm².

3.12 Example 12

In a polypropylene container, 48 g M200 were stirred in 220 g MEK at 20°C. leading to a clear solution. Similarly, 8 g MDEA, 4 g Kbenzoatesolution and 1 g acetic acid were dissolved in 220 g MEK to obtain asecond solution. The solutions were combined in a rectangular container(20×20 cm×5 cm height) by pouring one solution into the other, which ledto a homogeneous mixture of low viscosity. The container was closed witha lid and the mixture was gelled at room temperature for 24 h. Theresulting monolithic gel slab was dried through solvent extraction withscCO₂ in a 25 l autoclave leading to a porous material.

The compressive strength was determined according to DIN EN ISO 844 with6.3% strain.

The elastic modulus was 12.52 N/mm².

3.13 Example 13

In a polypropylene container, 48 g M200 were stirred in 220 g MEK at 20°C. leading to a clear solution. Similarly, 8 g MDEA, 4 g Kbenzoatesolution and 1 g propionic acid were dissolved in 220 g MEK to obtain asecond solution. The solutions were combined in a rectangular container(20×20 cm×5 cm height) by pouring one solution into the other, which ledto a homogeneous mixture of low viscosity. The container was closed witha lid and the mixture was gelled at room temperature for 24 h. Theresulting monolithic gel slab was dried through solvent extraction withscCO₂ in a 25 l autoclave leading to a porous material.

The compressive strength was determined according to DIN EN ISO 844 with6.0% strain.

The elastic modulus was 12.75 N/mm².

4. Results

TABLE 1 Results. Thermal conductivity Compressive Density [mW/m * K]strength [kg/m³] (p = 1 bar, T = 10° C.) [kPa] Example 1 (comparative)105 18.9 338 (8 g MDEA, 1 g Ksorbate solution) Example 2 107 18.5 353 (8g MDEA, 1 g Ksorbate solution) + acetic acid Example 3 (comparative) 12118.5 561 8 g MDEA, 1 g Ksorbate solution, 6 g butanol) Example 4 12117.8 598 8 g MDEA, 1 g Ksorbate solution, 6 g butanol + propionic acid)Example 5 130 17.9 635 8 g MDEA, 1 g Ksorbate solution, 6 g BDeoA +propionic acid) Example 6 (comparative) Sedimentation of (8 g MDEA, 4 gKacetate solution, water) undissolved particles Example 7 111 18.8 484(8 g MDEA, 1 g Kacetate solution, water) + acetic acid Example 8 11718.2 571 (8 g MDEA, 1 g Kacetate solution) + acetic acid Example 9(comparative) Wet gel broken (8 g MDEA, 1 g K15,) Example 10 117 18.1443 (8 g MDEA, 1 g K15) + propionic acid Example 11 123 18.5 538 (8 gMDEA, 4 g Kbenzoate solution) Example 12 121 18.0 477 (8 g MDEA, 4 gKbenzoate solution) + acetic acid Example 13 121 18.0 509 (8 g MDEA, 4 gKbenzoate solution) + propionic acid

5. Abbreviations

H₂O Water

K15 Dabco K15 (PUR catalyst)

Ksorbate solution potassium sorbate dissolved in monoethylene glycol

Kacetate solution potassium acetate dissolved in tetraethylene glycol

Kbenzoate solution potassium benzoate dissolved in monoethylene glycol

M200 Lupranate M200 (polyisocyanate)

MEK Methyl ethyl ketone

MDEA 4,4′-Methylene-bis(2,6-diethylaniline)

1: A process for preparing a porous material, the process comprising: a)providing a mixture (I) comprising (i) a composition (A) comprisingcomponents suitable to form an organic gel and (ii) a solvent (B), b)reacting the components in the composition (A) in the presence of thesolvent (B) to form a gel, and c) drying of the gel obtained in step b),wherein the composition (A) comprises a catalyst system (CS) comprisinga catalyst component (C1) selected from the group consisting of alkalimetal and earth alkali metal, ammonium, ionic liquid salts of asaturated or unsaturated monocarboxylic acid and a carboxylic acid ascatalyst component (C2). 2: The process according to claim 1, whereinthe catalyst component (C1) is selected from the group consisting ofalkali metal and earth alkali metal, ammonium, ionic liquid salts of asaturated or unsaturated monocarboxylic acid with 2 to 8 carbon atoms.3: The process according to claim 1, wherein the catalyst component (C2)is selected from the group of saturated or unsaturated monocarboxylicacids with 2 to 12 carbon atoms. 4: The process according to claim 1,wherein the catalyst component (C1) is selected from the groupconsisting of alkali metal and earth alkali metal salts of a saturatedor unsaturated monocarboxylic acid with 2 to 8 carbon atoms and whereinthe catalyst component (C2) is selected from the group of saturated orunsaturated monocarboxylic acids with 2 to 12 carbon atoms. 5: Theprocess according to claim 1, wherein the catalyst system (CS) ispresent in the composition (A) in an amount in the range of from 0.1 to30% by weight, based on the total weight of the composition (A). 6: Theprocess according to claim 4, wherein the catalyst system (CS) comprisescatalyst components (C1) and (C2) in a ratio in the range of from 1:10to 10:1. 7: The process according to claim 1, wherein the composition(A) comprises at least one monool (am). 8: The process according toclaim 1, wherein the composition (A) comprises at least onepolyfunctional isocyanate as component (a1). 9: The process according toclaim 1, wherein the composition (A) comprises at least onepolyfunctional isocyanate as component (a1), and at least one aromaticamine as component (a2), optionally comprises water as component (a3),and optionally comprises at least one further catalyst as component(a4). 10: The process according to claim 9, wherein the at least onearomatic amine is a polyfunctional aromatic amine. 11: The processaccording to claim 9, wherein the at least one aromatic amine (a2) hasthe general formula I

where R¹ and R² can be identical or different and are each selectedindependently from among hydrogen and linear or branched alkyl groupshaving from 1 to 6 carbon atoms and all substituents Q¹ to Q⁵ and Q^(1′)to Q^(5′) are identical or different and are each selected independentlyfrom among hydrogen, a primary amino group and a linear or branchedalkyl group having from 1 to 12 carbon atoms, where the alkyl group canbear further functional groups, with the proviso that the compoundhaving the general formula I comprises at least two primary aminogroups, where at least one of Q¹, Q³ and Q⁵ is a primary amino group andat least one of Q^(1′), Q^(3′) and Q^(5′) is a primary amino group. 12:The process according to claim 1, wherein composition (A) comprises (a0)from 0.1 to 30% by weight of catalyst system (CS), (a1) from 25 to 94.9%by weight of at least one polyfunctional isocyanate, and (a2) from 0.1to 30% by weight of at least one polyfunctional aromatic amine havingthe general formula I

where R¹ and R² can be identical or different and are each selectedindependently from among hydrogen and linear or branched alkyl groupshaving from 1 to 6 carbon atoms and all substituents Q¹ to Q⁵ and Q^(1′)to Q^(5′) are identical or different and are each selected independentlyfrom among hydrogen, a primary amino group and a linear or branchedalkyl group having from 1 to 12 carbon atoms, where the alkyl group canbear further functional groups, with the proviso that the compoundhaving the general formula I comprises at least two primary aminogroups, where at least one of Q¹, Q³ and Q⁵ is a primary amino group andat least one of Q^(1′), Q^(3′) and Q^(5′) is a primary amino group, (a3)from 0 to 15% by weight of water, and (a4) from 0 to 29.9% by weight ofat least one further catalyst, in each case based on the total weight ofthe components (a0) to (a4), where the % by weight of the components(a0) to (a4) adds up to 100% by weight and wherein the sum of thecomponents (a0) and (a4) is in the range of from 0.1 to 30% by weightbased on the total weight of the components (a0) to (a4). 13: Theprocess according to claim 9, wherein the amine component (a2) comprisesat least one compound selected from the group consisting of3,3′,5,5′-tetraalkyl-4,4′-diaminodiphenylmethane,3,3′,5,5′-tetraalkyl-2,2′-diaminodiphenylmethane and3,3′,5,5′-tetraalkyl-2,4′-diaminodiphenylmethane, where the alkyl groupsin the 3,3′,5 and 5′ positions can be identical or different and areselected independently from among linear or branched alkyl groups whichhave from 1 to 12 carbon atoms and can bear further functional groups.14: The process according to claim 8, wherein component (a4) catalyzesthe trimerization to form isocyanurate groups. 15: The process accordingto claim 9, wherein component (a4) comprises at least one tertiary aminogroup. 16: The process according to claim 1, wherein no water is used.17: The process according to claim 1, wherein the drying according tostep c) is carried out by converting the liquid comprised in the gelinto the gaseous state at a temperature and a pressure below thecritical temperature and the critical pressure of the liquid comprisedin the gel. 18: The process according to claim 1, wherein the dryingaccording to step c) is carried out under supercritical conditions. 19:A porous material, which is obtained by the process according toclaim
 1. 20: A thermal insulation material, comprising the porousmaterial of claim
 19. 21: The thermal insulation material according toclaim 20, wherein the porous material is adapted to function as athermal insulation material for interior or exterior thermal insulationsystems. 22: The thermal insulation material according to claim 20,wherein the porous material is adapted to function as a thermalinsulation material for water tank or ice maker thermal insulationsystems.